THE AXTERIOR REGION OF THE SKULL. 219 



with the superior maxillary, the ethmoid with the lachrymal in front, and the 

 ethmoid with the sphenoid behind. 



The outer wall is formed in front by the orbital process of the malar bone ; 

 behind, by the orbital surface of the sphenoid. On it are seen the orifices of one 

 or two malar canals, and the suture connecting the sphenoid and malar bones. 



Angles. The superior external angle is formed by the junction of the upper 

 and outer walls : it presents, from before backward, the suture connecting the 

 frontal with the malar in front and with the great wing of the sphenoid behind : 

 quite posteriorly is the foramen lacerum anterius, or sphenoidal fissure, which 

 transmits the third, the fourth, the three branches of the ophthalmic division of 

 the fifth, the sixth nerve, some filaments from the cavernous plexus of the sym- 

 pathetic, the orbital branch of the middle meningeal artery, a recurrent branch 

 from the lachrymal artery to the dura mater, and the ophthalmic vein. The 

 nt'-rnal angle is formed by the junction of the upper and inner Avail, and 

 presents the suture connecting the frontal bone with the lachrymal in front and 

 with the ethmoid behind. The point of junction of these three sutures has been 

 named the dacryon. This angle presents two foramina, the anterior and posterior 

 ethrnoidal. the former transmitting the anterior ethmoidal vessels and nasal nerve, 

 the latter the posterior ethmoidal vessels. The inferior external angle, formed 

 by the junction of the outer wall and floor, presents the spheno-maxillary fissure, 

 which transmits the superior maxillary nerve and its orbital branches, the infra- 

 orbital vessels, and the ascending branches from the spheno-palatine or Meek el's 

 ganglion. The inferior internal <///<//. is formed by the union of the lachrymal 

 and os planum of the ethmoid with the superior maxillary and palate bones. 

 The '//<</>/'/'///. or base, of the orbit, quadrilateral in form, is bounded above 

 by the supraorbital ridge ; below, by the anterior border of the orbital plate of 

 the malar, superior maxillary, and its nasal process ; externally, by the external 

 angular process of the frontal and the malar bones ; internally, by the internal 

 angular process of the frontal and the nasal process of the superior maxillarv. 

 The circumference is marked bv three sutures, the fronto-maxillary internally, 

 the fronto-malar externally, and the malo-maxillary below : it contributes to the 

 formation of the lachrymal groove, and presents, above, the supraorbital notch 

 (or foramen), for the passage of the supraorbital vessels and nerve. The apex, 

 situated at the back of the orbit, corresponds to the optic foramen, a short, circular 

 canal, which transmits the optic nerve and ophthalmic artery. It will thus be 

 seen that there are nine openings communicating with each orbit viz. the optic 

 foramen, foramen lacerum anterius. spheno-maxillary fissure, supraorbital foramen, 

 infraorbital canal, anterior and posterior ethmoidal foramina, malar foramina, and 

 canal for the nasal duct. 



The Nasal Fossae. 



The Nasal Fossae are two large, irregular cavities situated on either side of the 

 middle line of the face, extending from the base of the cranium to the roof of the 

 mouth, and separated from each other by a thin vertical septum. They communi- 

 cate by two large apertures, the anterior nares. with the front of the face, and by the 

 two posterior nares with the pharynx behind. These fossae are much narrower 

 above than below, and in the middle than at the anterior or posterior openings ; 

 their depth, which is considerable, is much greater in the middle than at either 

 extremity. Each nasal fossa communicates with four sinuses, the frontal above, 

 the sphenoidal behind, and the maxillary and ethmoidal on the outer wall. Each 

 also communicates with four cavities: with the orbit by the lachrymal 

 groove, with the mouth by the anterior palatine canal, with the cranium by the 

 olfactory foramina, and with the spheno-maxillary fossa by the spheno-palatine 

 foramen : and they occasionally communicate with each other by an aperture in 

 the septum. The bones entering into their formation are fourteen in number : 

 three of the cranium, the frontal, sphenoid, and ethmoid, and all the bones of the 



